Method of Updating a Location Information Representing a Physical Location of a Communication Device, A Computer Program Product for Executing the Method, and a Communication System for Updating the Location Information

ABSTRACT

A method of updating a location information, which represents a physical location of a communication device (2), is generated by a location source (1), and sent from the location source (1) via a location object generating unit (1A, 2A) and a cache unit (3A) to a location consumer (4), comprises caching a first location information (6) in the cache unit (3A), monitoring of a second location information (60) received subsequently to the first location information (6) at the location object generating unit (1A, 2A) by the location object generating unit (1A, 2A) to detect an invalid location information, and, triggered by the detection of an invalid location information (30, 50, 70), sending a location object (31, 51, 61, 71, 81) generated by the location object generating unit (1A, 2A) from the location object generating unit (1A, 2A) to the cache unit (3A), wherein the location object (31, 51, 61, 71, 81) comprises an invalidation information (85-88) indicating that a location information (6, 83) sent prior to the location object (31, 51, 61, 71, 81) is invalid such that, when the location object (31, 51, 61, 71, 81) is received at the cache unit (3A), the cached first location information (6) is discarded by the cache unit (3A).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the United States National Phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP2013/000888, filed onMar. 22, 2013, and claiming priority to PCT International ApplicationNo. PCT/EP2012/003035, filed on Jul. 18, 2012; PCT InternationalApplication No. PCT/EP2012/003148, filed on Jul. 25, 2012; and PCTInternational Application No. PCT/EP2012/003543, filed on Aug. 21, 2012.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments relate to methods of updating a location information, whichrepresents a physical location of a communication device, which isgenerated by a location source, and which is sent from the locationsource via a location object generating unit and cache unit to alocation consumer. Embodiments further relate to a computer programproduct for executing such a method and to a communication system forupdating the location information.

Background of the Related Art

As part of presence conveyance a location may be associated with adevice and/or a user. The physical location of the device may berepresented by a location information provided in an element of thedevice such as a communication device, e. g. a mobile or an IP phone.Presence conveyance may be an important issue in emergency cases: thelocation information may be used by emergency services such as NG911(Next Generation 9-1-1) or NG112 (Next Generation 1-1-2) to locate thedevice that initiated an emergency communication request. Such alocation information may be expressed as civic location, e. g. a postaladdress, and/or as geospatial coordinates, e. g. a map location. Thephysical location of the device is required in order for a telephonyserver to locate a suitable emergency services number to be used toplace the call (routing). This number is obtained by interrogating aremote Location to Service translation server (LoST-server).

The standardization for NG911/NG112 requires the calling device, alsocalled endpoint, to convey the actual physical location during anemergency call. The calling device is further required to contact amapping service based on the latest location information in order toobtain routing information during start-up and immediately before theemergency call set-up, and to validate the latest location informationto ensure that the provided physical location is a valid and existingcivic address or map location during start-up and immediately before theemergency call set-up. While obtaining the routing information is donevia the LoST-server, validation is done via a Location ValidationFunction server (LVF-server) wherein the obtaining of the routinginformation and the validating of the latest location information may bedone by the mapping service comprising the LoST-server and theLVF-server. If the endpoint fails to contact the mapping service in timebefore an emergency call, the endpoint must use cached data.

In case of network environments, where the endpoint, which may be in theform of a SIP endpoint contacts the mapping service via a server, whichmay be in a form of a SIP-server, the server contacts the mappingservice on behalf of the registered endpoint. Updating the locationinformation cached by the server and/or by the endpoint may be achievedby conveying the physical location of the endpoint to the serverperiodically to keep the server updated before an emergency call is setup. For periodically updating the location information cached by theserver and/or by the device, a viable location source is required.Occasionally, the location source may be considered not to be viable.For example:

-   -   the location source does not respond to enquiries of the server        and/or of the device,    -   the location source does not send information in a timely        manner, for example within a periodic time interval,    -   the location source declares itself to not be viable,    -   the location source provides a null location which is not a        valid location information,    -   the location source ceases to provide location information, and    -   the location source provides an unrealistic location.

In the case of a not viable location source delivering not validlocation information, one way of improving the accuracy of the locationinformation is to attach an expiration date to the conveyed locationinformation. The expiration time may be computed and associated with alocation report received from a tracked entity as disclosed in US2003/0135486 A1. An analysis of a history of previous location reports,here, is utilized to estimate the relevance of future location reportsover time. By using the computed expiration time, an expiration timevalue acts as a threshold that controls the shape of a relevancedegradation curve of a location report. In KR 20040092579, a method forcorrecting a location estimation error of a user equipment in a CDMA(Code Division Multiple Access) system is described, wherein an accuratelocation of a user terminal is estimated by correcting a locationestimation error generated by a repeater. If a Base Transceiver Station(BTS) receives a message of an access channel for location registrationof a user equipment from a core network, the BTS detects timing when themessage of the random access channel is received, adds repeater passpath information to the message of the random access channel, andtransmits the message to a Base Station Controller (BSC). The BTSsearches for a repeater pass path of a signal received from the userequipment by using a stored message. The BSC estimates the location ofthe user equipment by using the retrieved repeater pass path informationand error information of the repeater.

While this prior art addresses the accuracy of future locationinformation based on stored location information presumed to be viable,these location estimate methods fail if the cached location information,on which the estimated location is based, is itself not viable or notvalid.

BRIEF SUMMARY OF THE INVENTION

Embodiments may provide an update of cached location information with animproved localization accuracy if subsequent to the caching of thelocation information a location source of the location informationbecomes not viable. The method of updating location information, whichrepresents a physical location of a communication device, is generatedby a location source, and sent from the location source via a locationobject generating unit and a cache unit to a location consumer,comprises caching a first location information in the cache unit,monitoring of a second location information received subsequently to thefirst location information at the location object generating unit by thelocation object generating unit to detect an invalid locationinformation, and, triggered by the detection of an invalid locationinformation, sending a location object generated by the location objectgenerating unit from the location object generating unit to the cacheunit, wherein the location object comprises an invalidation informationindicating that a location information sent prior to the location objectis invalid such that, when the location information is received at thecache unit, the cached first location information is discarded by thecache unit.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments and advantages of the invention are highlighted in thefollowing with respect to figures. For an improved clearness, thefigures are not true to scale or proportionate. In the figures, as longas not mentioned otherwise, same references indicate same parts withsame meaning. It illustrates:

FIG. 1a a schematic location conveyance system according to theinvention, wherein the location source is coupled to the communicationdevice which is coupled to the server,

FIG. 1b a schematic location conveyance system according to theinvention in another embodiment, wherein, in addition to the locationconveyance system of FIG. 1a , an alternative location source is coupledto the server,

FIG. 2 a schematic location conveyance system according to the inventionin another embodiment, wherein the location source is coupled to theserver,

FIG. 3a a schematic flow of messages from the location source to thecommunication device to the server comprising the cache unit to thelocation consumer,

FIG. 3b a schematic flow of messages according to the invention inanother embodiment, wherein, in addition to FIG. 3a , an alternativelocation source is replacing the location source,

FIG. 4 a schematic flow of messages according to the invention inanother embodiment, wherein the location source is comprised by alocation server comprising the location object generating unit,

FIG. 5 a schematic flow of messages according to the invention inanother embodiment, wherein, after discarding cached locationinformation, the caching of location information resumes based on validlocation information from the location source, and

FIG. 6 a location object comprising a retention-expiry element and atimestamp element according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

We provide a method of updating location information, which represents aphysical location of a communication device, is generated by a locationsource, and sent from the location source via a location objectgenerating unit and a cache unit to a location consumer, comprisescaching a first location information in the cache unit, monitoring of asecond location information received subsequently to the first locationinformation at the location object generating unit by the locationobject generating unit to detect an invalid location information, and,triggered by the detection of an invalid location information, sending alocation object generated by the location object generating unit fromthe location object generating unit to the cache unit, wherein thelocation object comprises an invalidation information indicating that alocation information sent prior to the location object is invalid suchthat, when the location information is received at the cache unit, thecached first location information is discarded by the cache unit.

The location information may be a value or a set of values related to acivic location or geospatial coordinates of a physical location. Thecivic location may be a postal address, wherein the geospatialcoordinates may define a map location. While the first locationinformation may be a civic location, the second location information maybe geospatial coordinates or vice versa. The communication device may bea mobile or stationary unit capable of sending and/or receiving dataover a communication connection. For example, the communication devicemay be a mobile phone, an IP phone, a Personal Digital Assistant, atablet PC, a laptop or the like. The communication device may also be astationary unit such as a desktop PC or a server. While each of theseunits is stationary by itself, it still may be movable by being operatedfor example on a car, boat, ship, bus, airplane or any other movablevessel.

The location source may be a GPS (Global Positioning System) sensor, atriangulation device and/or unit processing a position from severalreceived signals which have been received at a single device fromseveral wireless stations, respectively. The location source may also bea centralized data base which has stored civic addresses for multiplewired devices. In an office building, the civic address may be in theform of information about the building, a floor, and a room, e. g.building number, floor number, and room number. Thus, in networkenvironments, the location source may be a location server. The locationobject generating unit may be comprised by the communication devicewhose location information is generated by the location source.Alternatively, the location object generating unit may be comprised bythe location source itself. The cache unit may be comprised by a server,conveying the location information from the location source to thelocation consumer. Alternatively, the cache unit may be comprised by thecommunication device itself.

The location consumer may be the communication device or another deviceto which the location information is conveyed for providinglocation-based services. If a navigation system is to be used in amobile phone or smart phone comprising a GPS sensor, the location sourcein form of the GPS sensor, the location object generating unit, and thecache unit are comprised by the communication device, which is thelocation consumer as well. In a distributed system which is the caseoften in network environments, the location source may be external tothe communication device and embodied for example in a centralizedlocation/localization server. In NG911/NG112, the communication devicemay be the endpoint, for example a SIP endpoint, a unit for the mappingservice may be the location consumer and the server contacting themapping service on behalf of the registered endpoint may comprise thecache unit. If the communication device is connected to the locationsource, the location object generating unit would be comprised by thecommunication device, and, if the location source would be connected tothe server, the location object generating unit would be comprised bythe location source. The location information is cached on behalf of thecommunication device by the server that acts as a proxy for locationconveyance to the location consumer. If, after a location informationhas been cached by the server, the location source becomes notviable/valid, the (proxy) server should be informed so that the servercan determine if a previously cached location information is likely tostill be representative or, if this is not the case, an alternativelocation source to the location source should be sought by the server.

If the cache unit would be comprised by the location consumer, theconsumer should as well be informed of a not viable location source inorder to determine if the cached location information is stillrepresentative of the physical location of the communication device ornot. By monitoring of location information received subsequently to thecached location information by the location object generating unit anddetecting an invalid location information, the location objectgenerating unit is able to determine whether the location source isviable/valid or not. By monitoring the location information, thelocation object generating unit is able to detect the invalid locationinformation without or with little delay. Invalid location informationmay not only be false location information, but also non-locationinformation if location information is expected from the location objectgenerating unit. If there is a time interval within location informationis to be received lapses without receiving location information, thedetected location information is regarded invalid.

Triggered by the detection of the invalid location information, thelocation object generating unit sends a generated location object to thecache unit wherein the location object comprises an invalidationinformation which indicates that the location information sent prior tothe location object is invalid. By sending the invalidation informationfrom the location object generating unit to the cache unit, the serverand/or location consumer and/or the communication device, whichcomprises the cache unit, respectively, is informed that a cachedlocation information received prior to the location object is invalid,such that, when the location object is received at the cache unit, thecached location information is discarded. While the known standards forlocation conveyance do not consider the case when a previously conveyedlocation information is to be considered as being no longer valid, withthe exception of attaching an expiration information to the conveyedlocation information, the cached location information would be regardedvalid by the cache unit even though location information received aftercaching the location information would be discarded. With the invention,however, the validity of cached location information is addressed whensubsequently to the caching of the information the location source hasto be considered not viable due to sending of invalid locationinformation.

Independent of the reason of invalidation of the second locationinformation, the location object generating unit as the generator of thelocation object informs the cache unit which provides the locationinformation to the location consumer for executing location-basedservices, with the necessary invalidation information for the cache unitto discard the cached first information as being invalid locationinformation. In contrast to an expiration information, the invalidationinformation comprises an invalidation information relating not to thelocation information sent with the location object but to locationinformation sent prior to the location object. Therefore, theinvalidation information allows the cache unit the conclusion that witha not viable location source sending invalid location information,cached location information sent prior to the location source becomingnot viable, should be discarded since it is not secured that the cachedlocation information is still valid.

The location object may comprise a retention-expiry element indicatingthat, if a time value of the retention-expiry element has passed whenthe cache unit receives the location object, the cache unit discards thelocation object, and a timestamp element indicating a value of time whenthe location object is generated, and wherein the invalidationinformation is formed by setting the time value of the retention-expiryelement to be equal or earlier than the value of time of the timestampelement. The retention-expiry element and the timestamp element may beset by the location object generating unit or by a unit comprising thelocation object generating unit such as the communication device or thelocation source.

In the standard RFC 4119 (Request For Comments 4119) a retention-expiryelement as a field to a PIDF-LO (Presence Information DataFormat-Location Object) document that conveys the location information,is defined with regard to its use as: if the value in theretention-expiry element has already passed when the Location Recipientreceives the Location Object, the Recipient MUST discard the LocationObject immediately. The location object, which is sent as a PIDF-LOaccording to the standard RFC 4119, additionally to the retention-expiryelement contains a timestamp element indicating the time when thePIDF-LO document was created/generated. By setting the value of theretention-expiry element to be equal or earlier than the timestampelement/field, the device is effectively declaring that the locationinformation is effectively invalid for the cache unit and must bediscarded, even if the location information is held in the cache unit ascache location information received previously to the PIDF-LO document.While some standards specifying the conveyance of location informationmay not consider the case when a location information conveyedpreviously to a point in time when the location source has to beconsidered to be not viable, is to be considered as being no longervalid, the IETF standardization according to RFC 4119 can be used bysetting the time value of the retention-expiry element to be equal orearlier than the value of time of the timestamp element to illustratethe inventive approach to invalidate the previously conveyed locationinformation. A data type for the retention-expiry element according toRFC 4119 is specified in the W3C (World Wide Web Consortium) schemadefinition. The formal definition of the format of the retention-expiryelement is

<xs:element name=“retention-expiry” type=“xs:dateTime”minOccurs=“0”maxOccurs=“1”/>, wherein “xs:dateTime” is defined in the W3C schema. Noother type of format for the retention-expiry element is allowedaccording to RFC 4119. While according to the definition of theretention-expiry element according to RFC 4119 it is possible to achievethe desired effect of sending the invalidation information indicatingthat the location information sent prior to the location object isinvalid then the value of the retention-expiry element is set later thanthe value of the timestamp as long as the PIDF-LO document is receivedat the cache unit before the point in time set with the value of theretention-expiry element. However, according to the invention the valueof time of the timestamp element is relevant rather than the point intime of receipt of the PIDF-LO at the cache unit.

In another embodiment, the location object comprises the invalidationinformation in an invalidation information field indicating by singlevalue such as a flag, whether the location information sent prior to thelocation object is invalid or not. The single value may be set to zeroindicating invalid location information. Alternatively, a flag could beset such that a set flag indicates invalid location information.

In another embodiment, the location object comprises the locationinformation sent prior to the location object from the location objectgenerating unit to the cache unit in a form readable by the cache unitto enable the cache unit to confirm that the cached first locationinformation is the location information to be discarded. The locationobject may comprise the location information sent prior to the locationobject from the location object generating unit to the cache unit in alocation-info element distinguishing the location information sent priorto the location object from the invalidation information. Thelocation-info element according to RFC 4119 may be used for containingthe location information sent to the cache unit prior to the locationobject to allow the cache unit or a larger unit comprising the cacheunit such as a server or the location consumer or the communicationdevice to confirm the cached location that is to be discarded.

With the inclusion of the location information sent prior to thelocation object in the location object the cache unit is enabled toconfirm the cached location information to be discarded. If the cachedlocation information differs from the location information sent prior tothe location object and being comprised by the location object, thecache unit or the larger unit comprising the cache unit may request thelocation object generating unit to repeat the sending of the locationobject comprising the invalidation information. Before receiving anotherlocation object comprising invalidation information, the cached locationinformation may not be discarded.

The invalid location information may be detected as a result of thelocation source

-   -   not responding to enquiries of an enquiring unit, such as the        communication device, the location object generating unit, the        cache unit, the location consumer, or another unit enquiring        location information of the communication device,    -   not sending the location information in a timely manner,        specially within a value of the time interval predetermined by        the enquiring unit    -   declaring itself to not be viable,    -   providing as the location information a null location,    -   ceasing to provide the location information, or    -   providing an unrealistic location information.

Another form of location information being regarded by a skilled personas invalid location information may be an information sent from thelocation source to the location object generating unit that the locationsource is not viable. It is also possible that a manual misconfigurationof a location/localization server is regarded invalid locationinformation by the location object generating unit. By sending theinvalidation information triggered by the detection of the invalidlocation information from the location object generating unit to thecache unit, the cached first location information is caused to bediscarded, which fulfills the inventive ability to allow the locationsource of the communication device to declare that the location sourcehas become invalid and any location information provided prior to thepoint in time when the location source became invalid should not beused.

In another embodiment, if the detection of the invalid locationinformation by the location object generating unit ends, a thirdlocation information received subsequently to the second locationinformation at the location object generating unit is cached in thecache unit. Therefore, when the location object generating unit nolonger sends location objects comprising the invalidation information,the cache unit resumes caching location information to be able toprovide the location consumer with location information for executinglocation-based services.

A cache controlling unit may be coupled to the cache unit and may be atleast partially comprised by the communication device, a server actingas a proxy for location conveyance to the location consumer, or by thelocation consumer. Both, the cache controlling unit and the cache unitmay be comprised by the communication device, the server, or by thelocation consumer. A cache controlling unit distributed over thecommunication device, the server, and the location consumer or at leasttwo of these entities is possible. The cache controlling unit maycomprise the cache unit.

If the cached first location information is discarded by the cache unit,the cache controlling unit instead of receiving the location informationfrom the location source via the location object generating unit, mayreceive the location information from an alternative location source tothe location source, the alternative location source being internal orexternal to the cache controlling unit. As the location source, thealternative location source may be internal in form of an extension toLLDP called LLDP-MED (Link Layer Discovery Protocol-Media EndpointDevices), DHCP (Dynamic Host Configuration Protocol), enterprise server,manual means, etc. External forms of the alternative location source (orthe location source) include GPS, network-calculated locationinformation, etc.

In another embodiment, the reception of the location information fromthe location source is switched by the cache controlling unit to thereception of the location information from the alternative locationsource such that during switching the location consumer is supplied withthe location information without signaling a malfunction. Due to themonitoring of the second location information and sending of thelocation object comprising the invalidation information triggered by thedetection of the invalid location information by the location objectgenerating unit, the cache controlling unit is enabled to switch fromthe not viable location source to a viable alternative location sourcequickly enough such that during the switching the location consumer canbe supplied with continuous location information without signaling amalfunction.

A computer program product for executing the inventive method asoutlined above may be provided. The computer program product may be asoftware product comprising instructions. The computer program productmay be comprised by a machine readable medium wherein the machinereadable medium may be a floppy disk, a CD (Compact Disc), a DVD(Digital Versatile Disc), or any other suitable digital or analoguemedium.

The invention further comprises a communication system for updating alocation information, which represents a physical location of acommunication device, is generated by a location source, and sent fromthe location source via location object generating unit and a cache unitto a location consumer. The communication system comprises the cachingunit configured to cache a first location information in the cache unit,and the location object generating unit configured to monitor a secondlocation information received subsequently to the first locationinformation at the location object generating unit to detect an invalidlocation information, wherein the communication system is configuredsuch that, triggered by the detection of an invalid locationinformation, a location object generated by the location objectgenerating unit is sent from the location object generating unit to thecache unit, wherein the location object comprises an invalidationinformation indicating that a location information sent prior to thelocation object is invalid such that when the location object isreceived at the cache unit, the cached first location information isdiscarded by the cache unit.

The communication device may be a mobile phone, a wired phone, such asan office phone, a PDA (Personal Digital Assistant), a PC (PersonalComputer), a tablet PC or any other communication device comprising theapparatus features as outlined above. The first location informationand/or the second location information may be provided by locationsources such as a DHCP supporting server/switch, an LLDP-MED supportingLAN (Local Area Network), server/switch or an external configurationmanagement system. LLDP-MED—as mentioned above—is an enhancement ofLLDP. LLDP-MED has been registered by the Internet Assigned NumbersAuthority (LANA) as a valid value of a method element as defined by RFC4119 as an optional “method” element describing the way a locationinformation is derived or discovered. The location source may provide amanually configured value for a location information and/or comprise aGPS sensor or a base station processing several signal strengths ofsignals of the communication device received by several receiving unitsbeing located at different positions from each other. An internal(LLDP-MED, DHCP, enterprise server, manual means, etc.) or an externallocation source (GPS, network calculated location information, etc.) isthus possible.

In an embodiment of the communication system, the location object isconfigured to comprise a retention-expiry element indicating that, if atime value of the retention-expiry element has passed, then the cacheunit receives the location object, the cache unit discards the locationobject, and a timestamp element indicating a value of time when thelocation object is generated, wherein the retention-expiry element andthe timestamp element are configured such that the time value of theretention-expiry element is set to be equal or earlier than the value oftime of the timestamp element to form the invalidation information.

In FIG. 1a , a location source 1, for example in the form of a GPSsensor in a layer 2 switch (data link layer according to the OSI-7-LayerModel (Open Systems Interconnection Reference Model) is connected to acommunication device 2 called target device, having a physical locationwhich is represented by location information 6 provided by the locationsource 1. The location information 6 may be in any format or be in formof data to calculate the location information from. The communicationdevice 2 comprises a location object generating unit, called LOgenerator, 2A which generates/creates a location object, e.g. a PIDF-LO,7, which is sent from the communication device 2 to a server 3comprising a cache unit, called cache, 3A. The server 3 comprises acache controlling unit (not shown) which is coupled to the cache unit 3Afor controlling the cache unit 3A.

The location object 7 comprises a timestamp and a retention-expiryelement, wherein a time value of the retention-expiry element is set tobe equal or earlier than a value of time of the timestamp element sincethe location information 6 has been detected to be no longer valid bythe location object generating unit 2A. The location object 7 maycomprise a timestamp and a retention-expiry element, wherein a timevalue of the retention-expiry element is set to be equal or earlier thana value of time of the timestamp element should the location information6 be detected to be no longer valid by the location object generatingunit 2A. Triggered by the detection of the invalid location informationthe location object 7 comprises an invalidation information indicatingthat a location information sent prior to the location object 7 to thecache unit 3A comprised by the server 3, such that, when the locationobject is received at the cache unit 3A, cached location information inthe cache unit 3A is discarded by the cache unit 3A.

The server 3 acts as a proxy for location conveyance to a locationconsumer 4 which is coupled to the server 3 such that the server 3provides location information 8 to the location consumer 4 if the server3 is enquired to by the location consumer 4. The server 3 may cache thelocation information in the cache 3A to find a route for callssubsequent to a registration of the communication device 2 at the server3. For example, a mapping service may be provided by the server 3 onbehalf of a registered communication device 2 in form of a SIP endpoint,wherein the location consumer 4 is the communication device 2 enquiringthe server for mapping based on a latest location information in orderto obtain routing information during start-up and immediately before thecommunication device 2 setting up an emergency call. As the server 3,the location consumer may as well cache the location informationreceived. The PIDF-LO may comprise location information generated by thelocation source 1 to be cached in the cache unit 3A of the server 3.

In FIG. 1b , a schematic arrangement of a location conveyance system ofFIG. 1a is extended by an alternative location source 10 which iscoupled to the server 3 comprising the cache controlling unit and sendssecond location information 6A to the server 3 which discarded cachedlocation information in the cache unit 3A, because a location objectcomprising invalidation information 7 has been sent from thecommunication device 2 to the server 3 triggered by the detection ofinvalid location information from the location source 1. The alternativesource 10 may be a location server that stores location information forseveral or all communication devices of a network (not shown).

The location information 6A sent from the alternative location source 10to the server 3 may be configured manually and may therefore be lessreliable than the location information 6 of the primary location source1, which may determine location information automatically. Thealternative location source 10 therefore acts as a backup locationsource for the location source 1 only in cases where the location source1 becomes not viable/reliable which is indicated by the location object7 comprising invalidation information which indicates that the locationinformation 6 sent prior to the location object is invalid such thatwhen the location object is received at the cache unit 3A, the cachedlocation information in the cache unit 3A is discarded by the cache unit3A. As a consequence, instead of location information 6 from thelocation source 1, location information 6A from the alternative locationsource 10 is conveyed to the location consumer 4.

In FIG. 2, another location conveyance system according to the inventionis configured such that the location source 1 comprising a locationobject generating unit 1A is connected to the server 3, which comprisesthe cache controlling unit, and sends the location object comprisinginvalidation information to the server 3 in the case, where invalidlocation information has been detected by the location object generatingunit 1A which monitors location information received from the locationsource 1. The reception of the location information from the locationsource 1 at the location object generating unit 1A occurs internally ofthe location source 1. With the location source generating the inventivelocation object 6C which comprises an invalidation information in thecase of detecting invalid location information, the location source 1may be in the form of a central location server that provides the server3 directly with location information conveyed by location objects. Theserver 3 may inform the communication device 2 about locationinformation received by the location source 1. The server 3 may informthe communication device 2 if the location information of the locationsource 1 has become invalid (see arrow 9 in FIG. 2). Based on thereceived information that the location source 1 has become invalid, thecommunication device 2 may send an information 7A to the server 3, whichuses the cached location information in the cache 3A to provide locationinformation 8 to the location consumer 4.

In FIG. 3a , first embodiment of a schematic flow of messages accordingto the invention between the location source 1, the communication device2, the server 3 comprising the cache unit and the cache controllingunit, and the location consumer 4 is depicted. The communication device2 is embodied as a SIP endpoint while the server 3 is in the form of aSIP-server acting as a proxy for location conveyance to the locationconsumer 4. According to the downward arrow “t” the messages between thelocation source 1, the SIP endpoint 2, the SIP-server 3, and thelocation consumer 4 are exchanged from top to bottom on a time scale. Ina first message a location information 6 is provided from the locationsource to the SIP endpoint 2, which obtains the location information 6.For registering the SIP endpoint 2 at the SIP-server 3, the SIP endpoint2 creates a PIDF-LO document comprising valid location information.

The SIP endpoint 2 conveys the PIDF-LO document to the SIP-server 3 in aSIP register request comprising the PIDF-LO with a timestamp, 17. TheSIP-server 3 may cache the PIDF-LO, e. g. in order to collectlocation-based routing data necessary to route a call of the SIPendpoint 2 to the location consumer 4, 23. By sending a SIP inviterequest message from the SIP endpoint 2 to the server 3, 27, wherein theSIP invite message comprises a PIDF-LO with a timestamp, the SIPendpoint 2 sets up a call with a PIDF-LO comprising valid locationinformation 6. The server 3 forwards the call requested by the SIPendpoint 2 at the server 3 to the location consumer 4 by using thecached PIDF-LO for routing. For forwarding the call, the SIP-server 3sends a SIP invite request message with a PIDF-LO comprising validlocation information 6 with a timestamp 28, to the location consumer 4.Subsequently to the registration of the SIP endpoint 2 at the SIP-server3, the location information expires and is not updated, 29. As aconsequence, no location information is sent from the location source 1to the SIP endpoint 2, 30. The missing location information, 30, of thelocation source 1 is detected at the SIP endpoint 2 as invalid locationinformation. Triggered by the detection of the invalid locationinformation from the location source 1, the SIP endpoint 2 generates alocation object in form of a PIDF-LO wherein a timestamp element of thelocation object and a retention-expiry element are comprised by thelocation object.

A value of time of the timestamp is set to be equal to a value of timeof the retention-expiry element, 31. In a next SIP register message, theSIP endpoint 2 sends the PIDF-LO comprising invalidation informationwhich indicates that a location information sent prior to the locationobject is invalid to the SIP-server 3. When the location objectcomprising the invalidation information is received at a cache unitcomprised by the SIP-server 3, the SIP-server is not only prevented tocache the PIDF-LO, but the cache unit of the SIP-server discards thelocation information cached in the cache unit in form of the PIDF-LOreceived in the initial SIP register request message, 17. As a result ofthe discarded cached location information, location-based routing is notpossible unless the SIP endpoint 2 provides another PIDF-LO comprisingvalid location information, 32.

In FIG. 3b , in addition to the message flow of FIG. 3a , the SIP-server3, which comprises the cache unit and the cache controlling unit (notshown), contacts an alternative location source 1A replacing thelocation source 1. As the SIP-server 3 is informed by the SIP endpoint 2with the SIP register request message, 31, comprising a PIDF-LO with atimestamp and retention-expiry element, respectively, set to an equalvalue of time, the SIP-server 3 not only discards the cached locationinformation 6 in its cache but removes the PIDF-LO comprising thelocation information from the cache, 32. Instead of being unable toroute a call from the SIP endpoint 2 to the location consumer 4, theSIP-server 3 looks for alternative location sources, 33.

Triggered by the location object comprising the invalidation informationindicating that a location information sent prior to the location objectis invalid, 31, the server 3 contacts the alternative location source 1Aby sending a request message 34 from the SIP-server 3 to the alternativelocation source 1A. The alternative location source 1A may be a locationserver that has stored preconfigured location information which is morecoarse, e.g. localization tolerance+/−10 m instead of +/−3 m for thelocation source 1, or less reliable, e.g. an update time interval of 1day instead of 1 hour for the location source 1, than the locationinformation 6 of the location source 1. As the alternative locationsource 1A is able to provide valid location information, 35, to theSIP-server 3, the SIP-server 3 creates and caches a PIDF-LO comprisingvalid location information 35, 36. When the SIP endpoint 2 sets up acall by sending a SIP invite request message, 37, to the SIP-server 3,the SIP-server 3 has valid location information cached in its cache toadd the cached PIDF-LO either to a SIP invite message of the server 3 tothe location consumer 4 in response to the received SIP invite message,37, or to the SIP invite message, 37, from the SIP endpoint 2 forforwarding to the location consumer 4, 38.

As a result of the valid location information, 37, from the alternativelocation source 1A, the SIP-server 3 is able to send a SIP inviterequest message to the location consumer 4 for routing the callrequested by the SIP endpoint 2 with the SIP invite message 37 based onthe location information 35 of the SIP endpoint 2. The PIDF-LO sent withthe SIP invite 39 from the server 3 to the location consumer 4 comprisesvalid location information 35 so that the call can be forwarded. Whenthe location information forwarded with the SIP invite 39 from theSIP-server 3 to the location consumer 4 becomes invalid, the SIP-server3 may inform the location consumer 4 about the PIDF-LO received by thelocation consumer 4 to become invalid if the location customer hasstored a PIDF-LO which is not the case in NG911 scenarios.

In the schematic flow of messages of FIG. 4 the location source 1 isembodied as a location server sending a PIDF-LO with a timestamp 6C tothe SIP-server 3 without an involvement of the communication device 2 inform of a SIP endpoint. The SIP-server 3 again comprises the cache unitand the cache controlling unit and obtains the PIDF-LO with location andtimestamp information of the SIP endpoint 2 from the location serverwhich may be a central location server. The SIP-server 3 caches/storesthe PIDF-LO received from the location source 1 for example to collectlocation-based routing data, 43.

By sending a SIP invite message 47 to the SIP-server 3, the SIP endpoint2 sets up a call to be forwarded by the SIP-server 3 to the locationconsumer 4. The SIP-server 3 inserts the stored PIDF-LO from its cachein a SIP invite request message 48 comprising a PIDF-LO with the storedlocation information for routing the call requested by the SIP endpoint2 to the location consumer 4 based on the location information providedby the location server 1. Subsequently to the SIP invite message 48 sentfrom the SIP-server 3 to the location consumer 4, the locationinformation expires and is not updated, 50. The location server 1invalidates the PIDF-LO by setting a value of time of a retention expiryelement equal to a value of time of a timestamp comprised by thePIDF-LO, 51.

The location source 1 in form of the location server may calculate thelocation information of the SIP endpoint 2 by using information from anetwork infrastructure. Invalidation of the location information sentfrom the location source 1 to the SIP-server 3 may be caused by missingnetwork data. Invalidation of the location information from the locationsource 1 may also be caused by location information that is mistyped byan administration authority. When the PIDF-LO is received at the cacheunit of the SIP-server 3, the cached location information is removed bythe SIP-server 3 by removing the PIDF-LO 6C from the cache 34. TheSIP-server 3 informs the SIP endpoint 2 and may inform the locationconsumer 4 about the invalidation of its cached location information,52. The SIP endpoint 2 is informed by a SIP message “Your locationexpired” 53 that is sent from the SIP-server 3 to the SIP endpoint 2that its location information has expired and is not valid anymore. Ifthe location consumer 4 has stored location information, the locationconsumer 4 is informed about the invalidation of its locationinformation due to the invalidation of the location information of theSIP endpoint 2 by the SIP-server 3 by another SIP message 61 whereinthis SIP message comprises a PIDF-LO with a value of time of aretention-expiry element being set equal to a value of time of atimestamp comprised by the PIDF-LO, 61.

The SIP message 51 or 61 each comprising the information of the aboutthe invalidation of the location information of the SIP endpoint 2 is amessage beyond the messages conventionally being exchanged within a SIPcall. Other protocols like HTTP (Hypertext Transfer Protocol) or SNMP(Simple Network Management Protocol) or other protocols may be choseninstead of the Session Initiation Protocol used by the SIP endpoint 2and the SIP-server 3 to exchange messages for executing the inventivemethod. At least the message that the location information 6C sent priorto the location object 51 is invalid may be exchanged via such aprotocol other than SIP.

In FIG. 5 a schematic flow of messages in another embodiment of theinvention between the location source 1, the communication device 2, theserver 3 comprising a cache unit and cache controlling unit, and thelocation consumer 4 as arranged in the location conveyance system ofFIG. 1a is shown. The location source 1 provides raw locationinformation 6 of the communication device 2 to the communication device2. Raw location information is defined as any location information thatwith or without processing allows the communication device 2 todetermine its physical location. The raw location information 6 may besent for instance as a PIDF-LO, in a data structure of a PIDF-LO, or inany other data format suitable for conveyance.

The communication device 2 that needs to convey its location to thelocation consumer 4 receives the initial raw location information 6 andsends this raw location information 6 to the server 3 acting as a proxyfor a location conveyance to the location consumer 4, 62. The server 3,called location proxy as the server 3 acts as a proxy for the locationconsumer 4, completes the raw location information 6 by adding atimestamp to the raw location information 6 and caches the completed rawlocation information as a location object in the cache unit of theserver 3, 63. As the communication device 2 detects a change in the rawlocation information 6 sent from the location source 1 to thecommunication device 2, the communication device 2 sends this changedraw location information 6 representing a changed physical location ofthe communication device 2 to the server 3, 62A. By sending the changedraw location information 6 to the server 3, the cached locationinformation in the cache unit of the server 3 is updated. The server 3completes the new/changed raw location information 6 by adding atimestamp and caches this new/changed raw location information 6 in itscache unit as the actual physical location of the communication device2, 63A.

Afterwards, the server 3 detects a condition where the location of thecommunication device 2 needs to be sent to the location consumer 4, 64.As the raw location information 6 did not change after the completedlocation information has been sent from the server 3 to the locationconsumer 4, the server 3 detects another condition where the physicallocation of the communication device 2 needs to be sent to the locationconsumer 4, 64, and therefore sends the same completed locationinformation cached in its cache unit to the location consumer 4, 64which has been sent before to the location consumer 4 (see timelineindicated by the arrow t). Afterwards, the communication device 2 onceagain detects a change in the raw location information 6 and updates thelocation information cached in the cache of the server 3, 62A, bysending the changed raw location information from the communicationdevice 2 to the server 3. As occurred before, the server 3 completes thenew/changed raw location information 6 by adding a timestamp and storesthe new/changed raw location information 6 as a location object in itscache unit, 63A.

Afterwards, the communication device 2 detects that the raw locationinformation 60—in contrast to the raw location information 6—from thelocation source 1 is no longer valid, 70, and updates the server 3 bysending a location object comprising an invalidation informationindicating that the location information 6 sent prior to the locationobject is invalid to the server 3 for updating the cached locationinformation 6 of the server 3, 71. The location object sent from thecommunication device 2 to the server 3, 71, is received at the cacheunit of the server 3 wherein the cached location information 6 isdiscarded by the cache unit of the server 3. As a result, the server 3will not use the location information 6 that it has stored/cached forthe communication device 2 and instead uses a default locationinformation for the communication device 2 that is stored in the cacheunit, 72.

Afterwards, the server 3 detects a further condition where the physicallocation of the communication device 2 needs to be sent to the locationconsumer 4 and sends (only) the default location information to thelocation consumer 4 instead of the previously cached completed locationinformation 6, 73. Although the default location information may be lessaccurate as the previously cached full location information 6 at thetime of caching, the server 3 uses the default location information asthe cached full location information 6 is considered to be notviable/valid. The default location information is considered a validlocation information and therefore sent to the location consumer 4 bythe server 3. Afterwards, another raw location information 66 from thelocation source 1 is detected by the communication device 2 as valid rawlocation information and therefore sent as raw location information fromthe communication device 2 to the server 3 as an update of the cacheddefault location information, 62B. The server 3 considers the rawlocation information 66 as valid location information and thereforecompletes the new/changed raw location information 66 by adding atimestamp and stores/caches the new/changed raw location information 66as a location object in its cache unit, 63A.

Other embodiments than that shown in FIG. 5 are possible: for example,the location source 1 may not repeatedly provide raw locationinformation 6. The communication device 2 may be able to complete theraw location information by adding a timestamp rather than leaving thecompletion of the raw information 6 as a task for the server 3 (see FIG.1b ). The communication device may detect a condition when the locationconsumer 4 requires the location of the communication device 2 and thecommunication device 2 may provide the condition to the server 3.However, if the server 3 needs to complete the raw location information6 from the communication device 2 by adding a timestamp for timecritical condition then the server 3 may instead of completing the(actual) raw location information from the communication device 2 stillchoose to use the already cached location information for forwarding tothe location consumer 4 even though this cached location information maybe of a previous date than the raw location information the server 3 isable to receive from the communication device 2.

As the already cached location information in the server 3 is used, atransfer time of the raw location information from the communicationdevice 2 to the server 3 and a processing time for completing this rawlocation information 6 by at least adding a timestamp is saved. Theserver may push the completed location information to the locationconsumer 4 but other implementation may allow the location consumer 4 topull the completed location information from the server 3. Thecommunication device 2 may not push the location information to theserver 3 but other implementations may allow the server 3 to pull thelocation information from the communication device 2 instead. Thelocation source is shown in FIG. 5 to push the location information tothe communication device 2 but other implementation may allow thecommunication device 2 to pull the location information from thelocation source 1. In some implementations, the communication device 2may have direct access to the location consumer 4. In theseimplementations, the server 3 acting as a proxy for the locationconsumer 4 on behalf of the communication device 2 is not required.

In FIG. 6 an embodiment of the inventive location object 81 comprisingan invalidation information 85 to 88 indicating that a locationinformation 83 sent prior to the location object 81 is invalid is shown.The location object 81 comprises a location-info-element/field 82comprising a civic address as the physical location of the communicationdevice 2 sent prior to the location object 81 from the location objectgenerating unit to the cache unit, 83. The location information 83 isreadable by the cache unit to enable the cache unit to confirm that thecached location information is the location information to be discardedas a result of the reception of the location object 81. Thelocation-info-element 82 is distinguished from the invalidationinformation 85 to 88. Therefore, the location-info-element distinguishesthe location information 83 sent prior to the location object 81 fromthe invalidation information 85 to 88.

The invalidation information 85 to 88 is embodied as a retention-expiryelement 87 according to the standard RFC 4119 comprising date and timeinformation 88 according to this standard. The date and time information88 constitutes a time value of the retention-expiry element 87. Theinvalidation information 85 to 88 comprises further a timestamp element85 indicating a value of time 86 when the location object 81 isgenerated. By setting the time value 88 of the retention-expiry element87 to be equal—as is the case in FIG. 6—or earlier than the value oftime 86 of the timestamp element 85, it is indicated that a locationinformation sent prior to the location object 81 is invalid such thatwhen the location object 81 is received at the cache unit, the cachedlocation information is discarded by the cache unit. The location-infoelement 82 therefore comprises the last provided location information 83to assist the server/location consumer/communication device to confirmthat a previously cached version of the location information 83 shouldbe discarded. The location object 81 also indicates the source of thelocation information 83 in a “method” element, 84, that no longerprovides valid location information. In FIG. 6, this source of invalidlocation information is “LLDP-MED” as comprised by the “method” element.The location source LLDP-MED may become not viable when it ceases toadvertise to the communication device a LID TLV which is a LocationIdentification Type/Length/Value according to the ANSI-TIA 1057-2006LLDP-MED specification. When the LLDP-MED ceases to advertise the LIDTLV the Time To Live for the TLV expires and the server/communicationdevice/location consumer is no longer able to trust the previouslyadvertised value of the TLV. In other embodiments of the locationobject, the location information 83 to be discarded may be missing. Anyformat of the invalidation information indicating that a locationinformation sent prior to the location object is invalid such that, whenthe location object is received at the cache unit, the cached locationinformation is discarded by the cache unit, may serve as a locationobject according to the invention.

A technical feature or several technical features which has/have beendisclosed with respect to a single or several embodiments discussedherein before, e. g. the alternative location source 10 in FIG. 1b maybe present also in another embodiment e. g. the location conveyancesystems depicted in FIG. 1a and/or FIG. 2, respectively, except itis/they are specified not to be present or it is impossible for it/themto be present for technical reasons.

1-15. (canceled)
 16. A method of updating location information, saidlocation information representing a physical location of a communicationdevice, wherein said location information is generated by a locationsource, and wherein said location information is sent from the locationsource to an electronic device having hardware comprising a processorand non-transitory memory, the method comprising: monitoring a secondlocation information received subsequently to a first locationinformation at the electronic device to detect an invalid locationinformation included in the second location information, and, upondetection of the invalid location information included in the secondlocation information, sending invalidation information indicating thatlocation information of the first location information is invalid sothat the first location information is discarded by non-transitorycomputer readable medium storing the first location information inresponse to the invalid location information
 17. The method of claim 16,wherein the invalidation information comprises: a retention-expiryelement indicating that, if a time value of the retention-expiry elementhas passed when the non-transitory computer readable medium receives theinvalidation information, the non-transitory computer readable mediumdiscards the invalidation information, and a timestamp elementindicating a value of time when the invalidation information isgenerated, and wherein the invalidation information is formed by settingthe time value of the retention-expiry element to be equal or earlierthan the value of time of the timestamp element.
 18. The method of claim17, wherein: the invalidation information comprises a location objectthat contains the invalidation information in an invalidationinformation field indicating by a single value whether the locationinformation sent prior to the location object is invalid.
 19. The methodof claim 16, wherein: the invalidation information comprises thelocation information sent prior to invalidation information to thenon-transitory computer readable medium in a form readable by thenon-transitory computer readable medium to enable the non-transitorycomputer readable medium to confirm that the first location informationis the location information to be discarded.
 20. The method of claim 16,wherein: the invalidation information comprises the location informationsent to the non-transitory computer readable medium in a location-infoelement distinguishing the location information sent prior to theinvalidation information from the invalidation information.
 21. Themethod of claim 16, wherein the invalid location information is detectedas a result of a condition selected from the group consisting of: thelocation source not responding to enquiries of at least one member ofthe group consisting of the communication device, the location objectgenerating unit, the non-transitory computer readable medium, and theelectronic device, the location source not sending the locationinformation within a value of a time interval predetermined by anenquiring unit, the location source declaring itself to not be viable,providing as the location information a null location, the locationsource ceasing to provide the location information, and the locationsource providing an unrealistic location information.
 22. The method ofclaim 16, comprising: caching in the non-transitory computer readablemedium, a third location information received subsequently to the secondlocation information at the location object generating unit whendetection of the invalid location information by the location objectgenerating unit ends.
 23. The method of claim 16, wherein a controllingunit is coupled to the non-transitory computer readable medium, andwherein the controlling unit is at least one member of the groupconsisting of part of the electronic device, and a server acting as aproxy for location conveyance to the electronic device.
 24. The methodof claim 23, comprising: the controlling unit receiving locationinformation from an alternative location source internal or external tothe controlling unit after the first location information is discardedin response to the detection of the invalid location informationidentified in the second location information.
 25. The method of claim24, comprising: switching, by the controlling unit, reception of thelocation information from the location source to reception of locationinformation from the alternative location source.
 26. A non-transitorymachine readable medium having a computer program stored thereon suchthat a communication device performs a method defined by the computerprogram when a processor of the communication device runs the computerprogram, the method comprising: monitoring a second location informationreceived subsequently to a first location information at thecommunication device to detect an invalid location information includedin the second location information, and, upon detection of the invalidlocation information included in the second location information,sending invalidation information indicating that location information ofthe first location information is invalid so that the first locationinformation is discarded by non-transitory computer readable mediumstoring the first location information in response to the invalidlocation information
 27. A communication apparatus for updating alocation information that represents a physical location of acommunication device generated by a location source, the communicationapparatus comprising: a processor connected to non-transitory memory,the communication apparatus configured to monitor a second locationinformation received subsequently to first location information todetect invalid location information included in the second locationinformation, and the communication apparatus configured such that alocation object in response to detection of the invalid locationinformation of the second location information received after the firstlocation information, wherein the location object comprises invalidationinformation indicating that stored first location information is to bediscarded so that the first location information is discarded fromnon-transitory memory in response to the location object.
 28. Thecommunication apparatus of claim 27, wherein a location objectgenerating unit generates the location object, the location objectgenerating unit comprising a component of the communication device or acomponent of the location source.
 29. The communication apparatus ofclaim 27, comprising: the non-transitory memory to store the firstlocation information.
 30. The communication apparatus of claim 27,wherein the location object comprises: a retention-expiry elementindicating that, if a time value of the retention-expiry element haspassed when a cache unit receives the location object the cache unitdiscards the location object, and a timestamp element indicating a valueof time when the location object is generated.
 31. The communicationapparatus of claim 30 wherein the retention-expiry element and thetimestamp element are configured such that the time value of theretention-expiry element is set to be equal or earlier than the value oftime of the timestamp element to form the invalidation information. 32.The communication apparatus of claim 16, wherein the location objectcomprises: a retention-expiry element indicating that, if a time valueof the retention-expiry element has passed when the location object isreceived, the location object is to be discarded, and a timestampelement indicating a value of time when the location object isgenerated; and wherein the retention-expiry element and the timestampelement are configured such that the time value of the retention-expiryelement is set to be equal or earlier than the value of time of thetimestamp element to form the invalidation information.
 33. Thecommunication apparatus of claim 27, wherein the communication apparatusis a mobile phone, a telephone device, a tablet personal computer, alaptop computer, a desktop computer, or a personal digital assistant.34. The communication apparatus of claim 27, wherein the apparatus is amachine selected from the group consisting of a computer device and aserver.